Hello,
The Emergency Signal and door lock/unlock button, both located next to eachother, suddenly stopped working. The car was parked and I can't think of any unusual driving/occurrence that would lead to it.
Any ideas of what the issue could be and how serious, $$ wise? Thank you in advance.

Sorry I was responding to the wrong question when I submitted my answer to you.
This is a common issue with the E46 chassis. The bottom of the button has tabs that hold the button together and they break overtime. The button actually should work electronically still but when the tabs break the button no longer makes contact when pressing on it. I recommend replacing the button. ..

The same thing happened on my 330i. The door lock / hazard switch is bad. It's cheap and easy to replace. I bought mine here. Came in a BMW box. To replace, you just need a pocket screwdriver and 10 minutes of time. http://www.partsgeek.com/catalog/2003/bmw/330i/body_electrical/hazard_flasher_switch.html